Objective: The aim of the present study was to evaluate the effects that inspiratory muscle training (IMT) and respiratory exercises have on muscle strength, peak expiratory flow (PEF) and severity variables in children with asthma. Methods: This was a randomized analytical study involving 50 children with asthma allocated to one of two groups: an IMT group, comprising 25 children submitted to IMT via an asthma education and treatment program; and a control group, comprising 25 children who were submitted only to monthly medical visits and education on asthma. The IMT was performed using a pressure threshold load of 40% of maximal inspiratory pressure (MIP). The results were evaluated using analysis of variance, the chi-square test and Fisher's exact test, values of p > 0.05 being considered significant. Results: In the comparative analysis, pre- and post-intervention values of MIP, maximal expiratory pressure (MEP) and PEF increased significantly in the IMT group: MIP from −48.32 ± 5.706 to −109.92 ± 18.041 (p < 0.0001); MEP from 50.64 ± 6.55 to 82.04 ± 17.006 (p < 0.0001); and PEF from 173.6 ± 50.817 to 312 ± 54.848 (p < 0.0001). In the control group, however, there were no significant differences between the two time points in terms of MIP or MEP, although PEF increased from 188 ± 43.97 to 208.80 ± 44.283 (p < 0.0001). There was a significant improvement in the severity variables in the IMT group (p < 0.0001). Conclusions: Programs involving IMT and respiratory exercises can increase mechanical efficiency of the respiratory muscles, as well as improving PEF and severity variables.

Keywords: Breathing exercises; Asthma/therapy; Asthma/rehabilitation.